In connection with the collection of tolls at toll bridges, turnpike entrances or exits, etc., vehicle classification typically is a manual function possibly in conjunction with a treadle arrangement or the like for making an axle count. Attempts to automate this procedure in the past have not proven particularly successful and/or economically justifiable, because of the wide variety of vehicle configurations, somewhat hostile working environments, etc. The present invention is directed to a novel, highly simplified and economical computer-based system for automatic classification of vehicular traffic. In one of its simplest forms, the system of the invention may be used principally as an auditing system against which to verify the toll receipts at a given booth. With relatively simple additions, however, the system can be adapted for automatic toll calculation for a variety of vehicles. In another alternative form, the classification system may be utilized without regard to toll collection and/or calculation to automatically control the flow of vehicular traffic. For example, the systems may be used to identify a passenger bus and admit it into a restricted traffic lane, while excluding vehicles of all other types.
The system of the invention makes use of a commercially available ultrasonic ranging unit, which is mounted directly above the vehicular traffic lane and arranged to transmit pulses of ultrasonic energy downward toward the roadway surface. When a vehicle transits the detection zone, the ranging unit repetitively samples the distance from the proper vehicle to the ranging unit. Individual readings can be processed in a variety of ways, to provide a profile of the vehicle, to determine its average height, and to determine maximum height of the vehicle. Particularly in respect to the latter, the system of the invention provides for successive height readings to be compared with prior and subsequent readings and for rejection of aberrational readings, such as might result from the presence of an upstanding post or the like on the vehicle, not actually representing a true height characteristic of the vehicle.
In accordance with one aspect of the invention, the ultrasonic ranging unit may be utilized in conjunction with a wheel-actuated treadle positioned in the roadway area slightly in advance of the ranging unit. The treadle mechanism may be utilized not only to activate the ranging unit, but also to provide an axle count in conjunction with the vehicle height profile information as part of the classifying information.
A microprocessor system, forming part of the invention, includes a programmable read-only memory (PROM or EPROM) preprogrammed with classification data for as many classes of vehicles as the operator desires to establish. In one version of the system of the invention, the input data from the passage of a vehicle under the ranging unit and axle counting treadle is referenced sequentially to the various pre-programmed classifications in the look-up table formed by the PROM or EPROM unit. When a satisfactory match is achieved, the vehicle classification data is output to whatever purpose and function is desired, whether it be merely auditing toll receipts, calculating tolls, regulating traffic flow, or the like.
With the system of the invention, the foregoing and many other functions may be performed in a highly reliable manner, with a system that is basically simplified and economical to install and operate.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments of the invention and to the accompanying drawings.